The present invention relates generally to electronic keyboard musical instruments, and more particularly to an improvement in casing structures of the electronic keyboard musical instruments.
In electronic keyboard musical instruments having a generally flat casing, the casing structure includes a bottom plate having a keyboard section placed thereon, a keyslip portion disposed right in front of the keyboard section, a pair of left and right side plates located close to the left and right sides of the keyboard section, and a roof plate forming a rear upper surface of the casing, and a bottom plate. However, when maintenance and inspection operations are to be performed on the interior of the casing, it is very troublesome to disassemble and then re-assemble the thus-constructed casing structure.
Japanese Utility Model Laid-open Publication No. SHO-62-103382 discloses an electronic keyboard musical instrument having an improved casing. The improved casing is composed of a main casing section and a rear casing section integrally forming a rear upper surface of the casing. The rear casing section is hinged to a bottom plate of the main casing section so that the rear casing section can be pivotally moved between open and closed positions. However, in assemblage of the casing, last screwing for fastening the rear casing section to the main casing section is performed, without exception, on the upper surface of the casing, so that the screw heads are inevitably exposed on the upper surface of the casing, presenting undesirable external appearance. Further, because the rear casing section is not detachably attachable to the main casing section in the disclosed casing, the assembling operations tend to be very troublesome, and maintenance and inspection of circuit boards etc. within the casing are also difficult to perform.
Further, in the electronic keyboard musical instruments of the above-mentioned types, the main circuit board is mounted on the bottom plate, for ease of the maintenance and inspection. However, where the main circuit board is to be mounted on the bottom plate near the back of the keyboard section, the bottom place must have an increased horizontal dimension in a front-and-back direction of the casing, which would therefore increase the overall horizontal dimension, in the front-and-back direction, of the keyboard musical instrument. Further, where the main circuit board is to be mounted on the bottom plate under the keyboard section, the overall vertical dimension or thickness of the keyboard musical instrument would increase.